I recently got some 510 Boge's to try. My usual carto's have been the 2.5Ω 808D's on my GLV2 mini. So far I'm finding that the 2.5Ω Boge's(have only tried one so far) are more sensitive to voltage drop off than the 808's. I am having to change out the batt. at about 3.8v's, where as the 808's are fine down to 3.5v . Is this normal for a Boge?